In the related art, a device in which a discoid cutting insert, which includes a cutting edge at an outer periphery edge is rotatably around an insert axial line thereof, is mounted on an insert attachment seat which is formed at an outer periphery portion of a distal end of a tool main body, which is rotated around a tool axial line, which is shown in for example, Patent Document 1 or 2, is known as a rotating-cutting-edge-type milling tool (a rotary milling tool) used for a milling process (a tool rotating cutting process) using a hard-to-cut material or the like such as a heat resistant alloy as a work material.
In the rotating-cutting-edge-type milling tool, among front and rear surfaces which face both sides of the cutting insert in the insert axial line direction, the front surface is located to face forward in a tool rotation direction around the tool axial line and is set to a rake face and the rear surface is located to face rearward in the tool rotation direction and sits on the insert attachment seat.
Also, at a time of cutting, the cutting insert is rotated around the insert axial line in a driven manner with respect to the insert attachment seat using force received by the cutting edge (which is cutting force or cutting resistance and includes cutting edge force or a component of edge force) when the cutting insert cuts into a work material. Thus, only a predetermined portion of the cutting edge is suppressed from being continuously used for cutting, and a decrease in partial sharpness of the cutting edge, cutting edge loss, and the like are prevented.